I Thought That One Of The Benefits Of Carrying A Smartphone Is That You No Longer Needed A Watch

I stopped wearing a watch about ten years ago. I don’t even remember whether it was because the battery on my watch failed or because I forgot how to adjust the watch for Daylight Savings time.  I moved on. The only task I needed a watch for was recording my runs and it did not take to long for me to enjoy running with my smartphone. So if I am a happy camper with my smartphone, why do I need an Apple or Google watch that does the same things as my smartphone but on even smaller screen?